914. X of a Kind in a Deck of Cards

#### QUESTION:

In a deck of cards, each card has an integer written on it.

Return `true` if and only if you can choose `X >= 2` such that it is possible to split the entire deck into 1 or more groups of cards, where:

• Each group has exactly `X` cards.
• All the cards in each group have the same integer.

Example 1:

``````Input: [1,2,3,4,4,3,2,1]
Output: true
Explanation: Possible partition [1,1],[2,2],[3,3],[4,4]
``````

Example 2:

``````Input: [1,1,1,2,2,2,3,3]
Output: false
Explanation: No possible partition.
``````

Example 3:

``````Input: [1]
Output: false
Explanation: No possible partition.
``````

Example 4:

``````Input: [1,1]
Output: true
Explanation: Possible partition [1,1]
``````

Example 5:

``````Input: [1,1,2,2,2,2]
Output: true
Explanation: Possible partition [1,1],[2,2],[2,2]
``````

Note:

1. `1 <= deck.length <= 10000`
2. `0 <= deck[i] < 10000`

1.计算出所有数字的数量

2.找出那个公约数

#### SOLUTION:

``````class Solution {
public boolean hasGroupsSizeX(int[] deck) {
if(deck.length<2) return false;
Map<Integer,Integer> table = new HashMap<>();
for(int i = 0;i<deck.length;i++) table.put(deck[i],table.get(deck[i])==null?1:table.get(deck[i])+1);
Set<Map.Entry<Integer, Integer>> entries = table.entrySet();
int smallest = Integer.MAX_VALUE;
for (Map.Entry<Integer, Integer> entry : entries) smallest = Math.min(smallest, entry.getValue());
ArrayList<Integer> list = hasGroupsSizeXHelper(smallest);
if (smallest < 2 || list.size() == 0) return false;
for (int i = 0; i < list.size(); i++) {
int index = list.get(i);
boolean tmp = true;
for (Map.Entry<Integer, Integer> entry : entries) {
if (entry.getValue() % index != 0){
tmp = false;
break;
}
}
if(tmp) return true;
}
return false;
}
public static ArrayList<Integer> hasGroupsSizeXHelper(int n){
ArrayList<Integer> integers = new ArrayList<>();
if(n <= 3){
return integers;
}